Field of the Invention
This invention relates generally to conveying systems having power-driven conveying sections and, more particularly, to apparatus for varying the effective length of the system by controlling the diversion of conveyed articles from one conveyor section to another.
Description of Prior Art
Many conveyor applications require that articles transported on one conveyor belt be transferred to another conveyor belt. Stationary rails spanning the conveying surfaces of the belts at a transfer point are often used for this purpose, particularly when the belts travel in opposite directions. In some applications, such as article accumulation, the transfer point can be moved. The moving transfer point allows the effective length of the conveying path and, consequently, the amount of articles accumulated to be controlled. In a spiral accumulator, such as that shown in U.S. Pat. No. 6,152,291, two parallel conveyor belts—an infeed belt and outfeed belt—are helically arranged with a rotatable transfer mechanism traveling between them. The position of the transfer mechanism depends on the relative speeds of the two oppositely-moving belts. A guide plate on the transfer mechanism directs articles from the infeed conveyor belt to the outfeed belt. A rotatable member in the transfer mechanism simultaneously engages drivers formed on the specially designed infeed and outfeed belts. The rotatable member, driven by the drivers, translates the transfer mechanism and its attached guide plate along the belts as determined by their relative speeds. The rotatable member rides along with the transfer mechanism.
A more common accumulation system is known as a bi-di (bi-directional) table. Typically, a bi-di table includes a bi-directional conveyor belt arranged to run perpendicular to a main conveyor belt. As articles build up on the main conveyor belt, backpressure directs them onto the bi-di belt, which runs in a direction away from the main conveyor. In this way, articles are accumulated on the bi-di belt's surface. As downstream processes require more articles, the direction of the bi-di belt is reversed so that the accumulated articles are pushed back onto the main conveyor belt. These bi-di tables, which support the bi-di belt and its drive mechanisms, are generally rectangular in shape with drive or idler shafts for sprockets or pulleys at each end. But, unlike the spiral accumulator, these simple, ubiquitous tables are not first-in, first out.
U.S. Pat. No. 6,497,321 and U.S. Pat. No. 7,222,723, both incorporated herein by reference, and related patents are directed to a first in, first-out accumulation system having a mechanism for diverting articles from one conveyor belt to another, in particular, oppositely-moving conveyor belts. In such systems, oppositely moving conveyor belts are traversed by a diverter that spans portions of both belts and is driven at a differential speed corresponding to the difference in speed between the oppositely moving conveyor belts. This machine works well for a wide range of applications, but the nature of the diverting mechanism requires that products being accumulated must flow into and out of the machine from the same end.
Therefore, there exists a need for a first in, first-out accumulation system having a mechanism for diverting articles from one conveyor belt to another when the belts are traveling in the same direction.